CN112442222A

CN112442222A - Plastic packaging material with antibacterial and fresh-keeping functions and preparation method thereof

Info

Publication number: CN112442222A
Application number: CN201910822588.1A
Authority: CN
Inventors: 丛怀涛
Original assignee: Beijing Jingzhaosuqi Technology Development Co ltd
Current assignee: Beijing Jingzhaosuqi Technology Development Co ltd
Priority date: 2019-09-02
Filing date: 2019-09-02
Publication date: 2021-03-05

Abstract

The invention provides a plastic packaging material with bacteriostatic and fresh-keeping functions and a preparation method thereof, wherein the plastic packaging material is prepared from 70-99% of plastic and 1-30% of nano functional material; the nanometer functional material is mainly prepared from the following nanometer raw materials: 1-10 parts of modified kaolin, 1-10 parts of nano zinc oxide, 1-10 parts of chitosan, 1-10 parts of starch, 1-10 parts of calcium carbonate, 1-10 parts of modified montmorillonite and 1-10 parts of anatase. The plastic packaging material has the comprehensive effects of reducing respiration, inhibiting bacteria, preventing mildew, eliminating dampness and decomposing ethylene, and achieves the effect of prolonging the food preservation period.

Description

Plastic packaging material with antibacterial and fresh-keeping functions and preparation method thereof

Technical Field

The invention relates to the technical field of plastic packaging, in particular to a plastic packaging material with antibacterial and fresh-keeping functions and a preparation method thereof.

Background

Nanotechnology, which began in the end of the 80 th 20 th century, is an emerging comprehensive technology that studies the characteristics of atoms, molecular structures, and their interaction principles on the nanoscale, and manipulates molecules, atoms, and even electrons directly on the nanoscale as needed to produce various specific products or create nanoscale processes. Nanomaterials bring scientific research from the macro to the micro domain, initiating a revolution in production, life science and technology, and human cognition.

Plastics are high molecular compounds (macromolecules) polymerized by addition polymerization or polycondensation reaction, commonly called plastics (plastics) or resins (resin), which can freely change components and shapes and forms, and are composed of synthetic resins and additives such as fillers, plasticizers, stabilizers, lubricants, pigments, etc. The plastic packaging material is mainly used in various packaging fields of family life, supermarket stores, hotels and restaurants and industrial production due to low cost and convenient processing. However, fresh fruits, vegetables, meats, frozen foods, deep-processed foods and the like are easy to breed bacteria and viruses after being stored in a plastic packaging film, the preservation time is short, and the long-term storage and transportation of the foods are not facilitated.

Disclosure of Invention

The plastic packaging material is used in the field of food preservation, so that nationwide transportation of fresh fruits and vegetables, meat, cakes and other products in a refrigerated state becomes possible, and the transportation cost and loss are greatly reduced.

The technical scheme of the invention is as follows:

the invention provides a plastic packaging material with antibacterial and fresh-keeping functions, which is prepared from 70-99% of plastic and 1-30% of nano functional material; the nanometer functional material is mainly prepared from the following nanometer raw materials: 1-10 parts of modified kaolin, 1-10 parts of nano zinc oxide, 1-10 parts of chitosan, 1-10 parts of starch, 1-10 parts of calcium carbonate, 1-10 parts of modified montmorillonite and 1-10 parts of anatase.

Preferably, at least one dimension of the nano functional material is within the range of 0.1-100 nm.

Preferably, the modified kaolin is obtained by ball milling modification of kaolin and hydrogen-containing silicone oil.

Preferably, the modified montmorillonite is obtained by ball-milling modification of sodium-based montmorillonite and hexadecyl trimethyl ammonium bromide.

Preferably, the ball milling medium is steel balls, the rotating speed is 800-1200 r/min, and the ball milling time is 1-2 hours.

Preferably, the plastic includes petrochemical-based biodegradable plastic and natural biodegradable plastic.

The invention also provides a preparation method of the plastic packaging material, which comprises the following steps:

(1) mixing chitosan, nano zinc oxide and starch at 60-70 ℃ by taking water as a medium to obtain a chitosan/nano zinc oxide/starch compound;

(2) stirring and mixing the modified kaolin, the calcium carbonate, the modified montmorillonite and the anatase with the compound obtained in the step (1), and grinding and sieving to obtain a sieved material;

(3) and melting and blending the sieved material and plastic to obtain the plastic packaging material master batch.

Preferably, in the blending process in the step (1), the mass percentage of water is 20-45%, and the pH value is 6-7.

Preferably, a dispersing agent is also added during the grinding in the step (2).

Further preferably, the sieved particle size in step (2) is less than 800 mesh.

Compared with the prior art, the invention has the advantages that:

the plastic packaging material of the invention has the functions of reducing respiration and inhibiting bacteriaThe five aspects of mildew prevention, dampness elimination, ethylene decomposition and the like are combined, and the effect of prolonging the preservation period of food is achieved. The plastic packaging material has the effects of mildew prevention and bacteriostasis, has obvious inhibition effect on various floras such as escherichia coli, staphylococcus aureus and the like, and has the sterilization rate of more than 88 percent. And can inhibit the activities of phenylalanine ammonia lyase, polyphenol oxidase and peroxidase. The active catalytic function of the plastic packaging material can decompose ripening gas such as ethylene and the like, and ethylene released in fruit and vegetable storage is oxidized and decomposed into CO₂And H₂O, reducing the ethylene content in the package. When the nanometer material quantum tunnel is used for packaging vegetables and fruits, stable entanglement generated by the nanometer material quantum tunnel carries out butterfly-shaped influence on water molecules, fibrin and electronic activity of the vegetables and fruits, so that the oxidation degree of the vegetables and fruits is released in an anion activity manner, and the oxidation resistance degree is improved by more than 560-800%. The plastic packaging material can enable vegetables and fruits to be in a dormant state, and the respiration is slowed down, so that the effects of prolonging the preservation time and improving the freshness and the taste are achieved.

The plastic packaging material can be made into soft packages such as preservative films, preservative bags and the like and hard packages such as preservative boxes and the like according to the requirements of packaging shapes by different processing technologies such as film blowing, bag making, blow molding, injection molding and the like. By applying the fresh-keeping package, the nationwide transportation of foods such as fresh fruits and vegetables in a refrigerated state becomes possible, the transportation cost and loss are reduced, and the huge profits are created for the upper, middle and lower reaches of an industrial chain.

Drawings

FIG. 1 shows the change of sugar degree of mature cherries stored in a common bag and a freshness protection package of the present invention at normal temperature;

FIG. 2 shows the change of sugar degree of the cherry stored in the ordinary bag and the fresh-keeping bag of the invention at normal temperature;

FIG. 3 shows the change of the sugar degree of the ripe cherries stored in the common bag and the freshness protection bag of the present invention under the refrigeration condition of 4 ℃;

FIG. 4 shows the change in the sugar content of the regular bag and the freshness protection package of the present invention storing nearly mature cherries under refrigeration at 4 ℃.

Detailed Description

The nano functional material has at least one dimension of 0.1-100 nm, more preferably 1-80 nm, and further 10-40 nm. The nanometer functional material can increase the dispersibility and the compatibility of the composite material in the particle size range, and improve the application effect of the composite material.

The plastic packaging material comprises 70-99% of plastic by mass, more preferably 80-90% of plastic by mass, and even more preferably 85% of plastic by mass. The plastic of the present invention is well known to those skilled in the art and includes Polyethylene (PE), polypropylene (PP), polyethylene terephthalate (PET), Low Density Polyethylene (LDPE), High Density Polyethylene (HDPE), Polystyrene (PS), etc. In the present invention, the plastic is preferably a degradable plastic, which means a polymer that undergoes a significant change in chemical structure and loses some properties and appearance after one or more steps under specified environmental conditions over a period of time. Typical degradable representative materials at present are petrochemical-based biodegradable plastics: such as Polycaprolactone (PCL), polybutylene succinate (PBS), adipic acid-terephthalic acid-butylene glycol copolymer (PBAT), polyvinyl alcohol (PVA), etc., and natural biodegradable plastics: such as polyhydroxyalkanoates (PHA, including PHB \ PHBV, etc.), polylactic acid (PLA), polypropylene carbonate (PPC), modified starch, etc. The degradable plastic is used as the base material to prepare the plastic packaging material, so that the environment-friendly performance is good, and the recycling of the material is facilitated.

The plastic packaging material also contains 1-30 wt% of nano functional material, preferably 5-25 wt%, and further 10-20 wt%. The addition of the nano functional material enables the plastic packaging material to have the effects of preventing mildew and bacteria and prolonging the preservation period.

The nano-scale raw material of the nano-functional material comprises modified kaolin, and the addition amount of the modified kaolin is preferably 3-8 parts by weight, and more preferably 5-7 parts by weight. Kaolin is a non-metallic mineral, a clay and claystone based on clay minerals of the kaolinite group. The chemical formula of the crystal is 2SiO₂·Al₂O₃·2H₂O, kaolin mineral belongs to 1:1 type layered silicate, the crystal mainly comprises silicon-oxygen tetrahedrons and Shaoxing-oxygen octahedrons, wherein the silicon-oxygen tetrahedrons are connected along two-dimensional directions in a mode of sharing a vertex angle to form a grid layer in hexagonal arrangement, and tip oxygen which is not shared by the silicon-oxygen tetrahedrons faces to one side; the 1:1 type unit layer is composed of the oxygen peaks of the common silicon oxygen tetrahedral layer and the oxygen attracting octahedral layer. The modified kaolin is obtained by ball-milling and modifying kaolin and hydrogen-containing silicone oil, wherein the mass ratio of the kaolin to the hydrogen-containing silicone oil is 10:1 to 3, and more preferably 10:1.2 to 1.8. The ball milling medium is preferably steel balls, the rotating speed is preferably 800-1200 r/min, more preferably 1000r/min, and the ball milling time is preferably 1-2 hours. After ball milling, the particle size of the kaolin is reduced, the specific surface area is increased, the hydrophobicity is enhanced, and the fusion capability of the kaolin and other raw materials is improved.

The nano-scale raw material of the nano-functional material comprises nano zinc oxide, and the addition amount of the nano zinc oxide is preferably 3-9 parts by weight, and more preferably 4-7 parts by weight. The nano zinc oxide has excellent antibacterial performance, and the antibacterial principle is from two points: one is a photocatalysis mechanism, namely, the nano zinc oxide can release electrons with negative electricity in water and air under the irradiation of sunlight, particularly ultraviolet light, and simultaneously leave holes with positive electricity to excite the air to generate active oxygen, and the active oxygen can generate oxidation reaction with various microorganisms, thereby achieving the sterilization effect. The other is a metal ion dissolution mechanism, namely, the dissociated zinc ions are combined with protease when contacting the bacterial body, so that the activity of the zinc ions is lost, and the bactericidal effect is achieved. The nano zinc oxide has the specific surface interface effect of the nano particles due to the particle size reaching the nano level, and is reflected in the aspect of antibacterial effect as follows: the number of surface atoms of the nano particles is greatly more than that of the traditional particles, and the surface atoms have high energy due to the lack of adjacent coordination atoms, so that the affinity of zinc oxide and bacteria can be enhanced, and the antibacterial efficiency is improved. The nano-zinc oxide is used in the nano-material, so that the defects and limitations of silver-series and titanium dioxide-series antibacterial agents such as easy discoloration and ultraviolet irradiation are overcome, and an excellent antibacterial effect is achieved. The source of the nano zinc oxide is not specially limited, and the nano zinc oxide can be obtained by adopting a commercial product.

The nano-scale raw material of the nano-functional material comprises chitosan, and the addition amount of the chitosan is preferably 2-7 parts by weight, and more preferably 4-6 parts by weight. Chitosan (chitosan), also known as chitosan, is obtained by deacetylation of chitin (chitin) widely existing in nature, and is chemically named polyglucosamine (1-4) -2-amino-B-D glucose. Because chitosan molecules have free amino groups, the chitosan molecules are easy to form salts in an acidic solution and have cationic property. The amino group characteristics of chitosan are more remarkable as the number of amino groups in the molecule of the chitosan increases, which is the basis of the unique properties of the chitosan, thereby laying the foundation of a plurality of biological characteristics and processing characteristics of the chitosan. The chitosan has good antibacterial activity and can inhibit the growth and reproduction of fungi, bacteria and viruses.

The nanometer functional material nanometer raw material comprises starch, and the adding amount of the starch is preferably 2-7 parts by weight, and more preferably 4-6 parts by weight. Starch is the polymerization of glucose molecules, which is the most common storage form of carbohydrates in cells. The starch is nano starch, and has the appearance characteristics that: the product is white, odorless, tasteless, and hygroscopic.

The nanometer functional material nanometer raw material comprises calcium carbonate, and the addition amount of the calcium carbonate is preferably 2-8 parts by weight, and more preferably 4-6 parts by weight. Calcium carbonate is an inorganic compound, the main components of which are: calcite, of the formula CaCO3, is neutral, substantially insoluble in water, and soluble in hydrochloric acid. The nano calcium carbonate is used in plastic, has high affinity with resin, and can raise or regulate the rigidity, toughness, bending strength, etc. of the material effectively. And can improve the rheological property of a plastic processing system, reduce the plasticizing temperature, and improve the dimensional stability, heat resistance and surface smoothness of a product.

The nanometer functional material nanometer raw material comprises modified montmorillonite, and the addition amount of the modified montmorillonite is preferably 3-8 parts by weight, and more preferably 4-6 parts by weight. Montmorillonite, a natural mineral of silicate, is the main mineral component of bentonite ore. Containing Al₂O₃ 16.54％，MgO 4.65％，SiO₂50.95 percent. Monoclinic system, multi-site microcrystals, aggregates in the form of soil, spheres, etc. The modified montmorillonite is obtained by ball milling modification of sodium-based montmorillonite and hexadecyl trimethyl ammonium bromide. The mass ratio of the montmorillonite to the hexadecyl trimethyl ammonium bromide is 10:1 to 3, and more preferably 10:1.2 to 1.8. The ball milling medium is preferably steel balls, the rotating speed is preferably 800-1200 r/min, more preferably 1000r/min, and the ball milling time is preferably 1-2 hours. The modified montmorillonite has strong adsorption capacity and good dispersion performance, and improves the impact resistance, fatigue resistance, dimensional stability, gas barrier performance and the like, thereby playing a role in enhancing the comprehensive physical properties of the polymer and improving the processing performance of materials.

The nano-scale raw material of the nano-functional material comprises anatase, and the addition amount of the anatase is preferably 3-8 parts by weight, and more preferably 4-6 parts by weight. Anatase is titanium dioxide (TiO)₂) One of the three minerals of (1). The product appearance was a white loose powder. The nano-scale titanium dioxide has high chemical stability, thermal stability, super-hydrophilicity and non-migration property, and can be used for long-term sterilization under the action of ultraviolet rays in light. The physical shielding type ultraviolet protective agent can absorb ultraviolet rays, reflect and scatter the ultraviolet rays and transmit visible light, has excellent performance and has great development prospect. Can be activated and generated under the action of ultraviolet rays in sunlight or lamp light to generate free radicals with high catalytic activity, can generate strong photooxidation and reduction capability, and can catalyze and photolyze a plurality of organic matters and partial inorganic matters attached to the surface of an object.

The invention also comprises a preparation method of the plastic packaging material with the antibacterial and fresh-keeping functions, which comprises the following steps:

In the invention, in the blending process in the step (1), the mass percent of water is preferably 20-45%, and more preferably 30-35%. The blending temperature is preferably 64-67 ℃, and the pH value is preferably 6-7.

In the present invention, it is preferable to further add a dispersant during the grinding in the step (2). The dispersant of the present invention is not particularly limited in kind, and may be any dispersant conventionally used in the art.

The method of the grinding and sieving is not particularly limited in the present invention, and the conventional grinding and sieving in the art is adopted. Wherein, the screened grain diameter in the step (2) is less than 800 meshes, and more preferably 1000-1200 meshes. The screened material is preferably treated with alcohol. The volume concentration of the alcohol is preferably 70-85%, and more preferably 75%. The invention washes and dries the material after alcohol treatment, and the material is used for melting and blending with plastic. The manner of washing, drying and melt blending is not particularly limited in the present invention, and conventional methods in the art can be used.

The plastic packaging material master batch prepared by the method can be prepared into flexible packages such as preservative films and preservative bags and hard packages such as preservative boxes according to the requirements of packaging shapes by different processing technologies such as film blowing, bag making, blow molding, injection molding and the like. By applying the fresh-keeping package, the nationwide transportation of foods such as fresh fruits and vegetables in a refrigerated state becomes possible, the transportation cost and loss are reduced, and the huge profits are created for the upper, middle and lower reaches of an industrial chain.

The technical solutions of the present invention will be described clearly and completely with reference to the following embodiments of the present invention, and it should be understood that the described embodiments are only a part of the embodiments of the present invention, and not all of the embodiments. All other embodiments, which can be derived by a person skilled in the art from the embodiments given herein without making any creative effort, shall fall within the protection scope of the present invention.

Example 1:

20g of kaolin and 1.2g of hydrogen-containing silicone oil are introduced into the pot of a planetary ball mill. 50 steel balls with different sizes are prepared in the tank body, the rotating speed of the main disc is controlled at 896r/min, and ball milling is carried out for 2 hours to obtain the modified kaolin.

20g of montmorillonite and 1.2g of cetyltrimethylammonium bromide were placed in the pot of a planetary ball mill. 50 steel balls with different sizes are prepared in the tank body, the rotating speed of the main disc is controlled at 896r/min, and ball milling is carried out for 2 hours to obtain the modified montmorillonite.

10g of nano chitosan, 10g of nano zinc oxide, 10g of nano starch and 20ml of water are mixed at 65 ℃, and the pH value of the mixed material is 7, so that the chitosan/nano zinc oxide/starch compound is obtained. Stirring and mixing 10g of modified kaolin, 10g of calcium carbonate, 10g of modified montmorillonite, 10g of anatase and 2g of dispersing agent with the chitosan/nano zinc oxide/starch compound, grinding and sieving with a 1000-mesh sieve, treating sieved materials with 75% alcohol, washing and drying with deionized water. And melting and blending the dried material and polyethylene according to the mass ratio of 1:9 to obtain the plastic packaging material master batch. And blowing the plastic packaging material master batch to obtain the plastic packaging freshness protection package.

Example 2

20g of kaolin and 1.5g of hydrogen-containing silicone oil are introduced into the pot of a planetary ball mill. 50 steel balls with different sizes are prepared in the tank body, the rotating speed of the main disc is controlled at 1126r/min, and the modified kaolin is obtained after ball milling for 1.5 hours.

20g of montmorillonite and 1.7g of cetyltrimethylammonium bromide were placed in the pot of a planetary ball mill. 50 steel balls with different sizes are prepared in the tank body, the rotating speed of the main disc is controlled at 11266r/min, and ball milling is carried out for 1.5 hours to obtain the modified montmorillonite.

10g of nano chitosan, 20g of nano zinc oxide, 10g of nano starch and 20ml of water are mixed at 70 ℃, and the pH value of the mixed material is 6.5, so that the chitosan/nano zinc oxide/starch compound is obtained. Stirring and mixing 10g of modified kaolin, 15g of calcium carbonate, 10g of modified montmorillonite, 10g of anatase and 2g of dispersing agent with the chitosan/nano zinc oxide/starch compound, grinding and sieving with a 1200-mesh sieve, treating the sieved material with 75% alcohol, washing and drying with deionized water. And melting and blending the dried material and polylactic acid according to the mass ratio of 3:7 to obtain the plastic packaging material master batch. And blowing the plastic packaging material master batch to obtain the plastic packaging freshness protection package.

Example 3

20g of kaolin and 1.8g of hydrogen-containing silicone oil are introduced into the pot of a planetary ball mill. 50 steel balls with different sizes are prepared in the tank body, the rotating speed of the main disc is controlled at 976r/min, and the modified kaolin is obtained after ball milling for 2 hours.

20g of montmorillonite and 1.8g of cetyltrimethylammonium bromide were placed in the pot of a planetary ball mill. 50 steel balls with different sizes are prepared in the tank body, the rotating speed of the main disc is controlled at 976r/min, and the modified montmorillonite is obtained after ball milling for 2 hours.

And (3) blending 20g of nano chitosan, 10g of nano zinc oxide, 10g of nano starch and 20ml of water at 65 ℃, wherein the pH value of the blended material is 7, so as to obtain the chitosan/nano zinc oxide/starch compound. 20g of modified kaolin, 10g of calcium carbonate, 10g of modified montmorillonite, 12g of anatase and 2g of dispersant are mixed with the chitosan/nano zinc oxide/starch compound by stirring, ground and sieved by a 1000-mesh sieve, and the sieved material is washed and dried by deionized water after being treated by 80 percent alcohol. And melting and blending the dried material and the modified starch according to the mass ratio of 2:8 to obtain the plastic packaging material master batch. And blowing the plastic packaging material master batch to obtain the plastic packaging freshness protection package.

Example 4

Selecting nearly mature commercial fresh cherries with consistent maturity, respectively packaging the cherries by using a common polyethylene plastic freshness protection package and the dormant freshness protection package in the embodiment 1 of the invention, and then carrying out physical and chemical component measurement at 0d, 2d, 4d, 6d and 8d, wherein the measured values are respectively weight loss rate, sugar degree and respiratory strength, and meanwhile, the sensory evaluation is assisted.

1. Appearance of the product

At the beginning of storage, the color maturity of cherries was consistent. When the sample is stored for 4 days at normal temperature, the color of the sample stored in the dormant freshness protection package is still bright and red. And 6d, storing at normal temperature, wherein the color of the cherry sample in the common fresh-keeping bag is obviously heavier than that of the cherry in the dormant fresh-keeping bag. From day 8, the cherry samples in the normal temperature normal freshness protection package decayed, while the cherry samples in the dormant freshness protection package of the present invention were intact and non-decayed.

2. Intensity of respiration

Under the test conditions, nearly ripe cherries were stored under ambient temperature conditions using a common plastic bag, and the amount released per kilogram per hour was found to be 300.99 mg after the in-system carbon dioxide concentration measurement. The dormant freshness protection package releases 152.07 mg of carbon dioxide per kilogram of mature samples per hour at normal temperature. It was determined from experimental measurements that the resting pouch did suppress the respiration intensity of the fruit to some extent.

3. Weight loss ratio

Tests show that the weight loss rate of the cherry sample preserved by the dormant preservative bag is lower than that of a common preservative bag, but the difference is not obvious.

4. Change result of sugar degree value

Under the condition of normal temperature, the storage period sugar degree value of the ripe cherries stored by the dormant freshness protection package is higher, which shows that the sugar degree of cherry samples stored by the dormant freshness protection package is gradually increased along with the prolonging of the storage time (see figure 1). When near-ripe cherries are stored, the brix value exhibits a steady decline (see fig. 2).

Under the condition of refrigeration at 4 ℃, the sugar degree of cherries stored by the common bag and the dormant freshness protection bag of the invention is obviously improved. For cherries that have fully matured, the normal bag is slightly higher than the dormant bag. But the differences were not significant from the data (see figure 3). However, for near-ripe cherries, the post-storage sweetness value of cherries stored in the resting pouch was higher, indicating that the sweetness of cherry samples stored in the resting pouch increased gradually with the increase in storage time (see fig. 4).

In summary, it can be seen that the dormant freshness protection package of the present invention can be used for storing nearly mature cherry samples, and the appearance color can be well maintained. The dormant freshness protection package can inhibit the respiratory intensity of the cherries to a certain extent, and the low-temperature storage mode is still a storage mode suitable for the cherries. The dormancy freshness protection package disclosed by the invention stores cherry samples, can prevent fruit and vegetable from losing weight to a certain extent, and pays attention to the sealing degree. Under the condition of normal temperature, the sugar degree of any fresh-keeping bag is stably increased, but under the condition of low temperature, the sugar degree value is rapidly increased.

Example 5

Preservation of Xinjiang small white apricot

Fresh picked Xinjiang small white apricots are respectively stored at normal temperature by using the freshness protection package and a common plastic bag. Each bag is filled with 500g of small white apricot, and the storage time is observed. The small white apricot pulp is soft and rotten and is crushed by hand.

The result shows that the small white apricots stored in the common plastic bag have the condition that the pulp becomes soft and rotten on the 6 th day; the small white apricots in the freshness protection bag of the invention are rotten by hand when stored for 15 days. The storage period of the fruits and the vegetables can be effectively prolonged by the freshness protection package.

Example 6

Preservation of tea

The tea leaves are put into the freshness protection package of the invention, the capacity is about 50g, and the freshness protection package is kept still for more than 30 minutes. Tea leaves of the same variety and batch are used as a comparison group, and the same amount of tea leaves are respectively taken to be brewed and tasted simultaneously, so as to compare the first soaking effect, the second soaking effect and the multi-soaking effect.

According to the comment of professional tea evaluators, after the freshness protection package is used, the fermented tea and the semi-fermented tea are rich in soup, rich in fragrance and sweet in taste; green tea, etc. is softer and more moist when being taken in mouth and better after being sweet. The freshness protection package can improve the quality of tea, and can keep freshness, resist bacteria, prevent moisture and prevent odor tainting.

Example 7

Preservation of traditional Chinese medicinal materials

The storage comparison test is carried out on the following 3 easily-damaged raw materials by using the freshness protection package of the invention, namely the raw malt, the rhubarb and the tuckahoe are respectively. 500g of each of the 3 batches was subjected to a first moisture test. 3 batches of 500g materials are divided into 2 parts, each 250g material is stored in a normal temperature warehouse (1), and one part is stored in a normal temperature warehouse (2) after being sealed by using the freshness protection package. After 23 days of storage, 2 material samples were separately moisture tested.

The results of the test of sample 23 at the later date are compared as follows:

the conclusion was compared by three sets of sample data:

1. the final moisture detection result of the material hermetically stored by using the freshness protection package is basically consistent with the result of the original material, no moisture changes exist, and the phenomenon of moisture absorption of the material is basically avoided.

2. The material that the conventionality was stored passes through 23 days's overcast and rainy day environment, and the moisture content that moisture detection result compares in the raw materials increases, appears the material phenomenon of absorbing moisture. The maximum change was no malting and the moisture increased by 1%. The fresh-keeping bag stores raw materials with volatile moisture, so that the moisture change of the stored materials caused by the change of the external environment can be inhibited.

3. The freshness protection package can play a drying and moisture-proof role in Chinese medicinal materials, flour, grains, nuts and the like, and prevent deterioration.

Example 8

Determination of antibacterial Activity of antibacterial preservative film of the present invention

The antibacterial preservative film of the invention is entrusted to the antibacterial material detection center of the research institute of physical and chemical technology of Chinese academy of sciences to measure the antibacterial activity value.

The detection basis is as follows: GB T31402-2015 test method for antibacterial property of plastic surface

Description of the samples: the control sample of the antibacterial preservative film disclosed by the invention is not standard PE.

And (3) detection results:

the antibacterial preservative film has good antibacterial performance, can be used for antibacterial preservation in the food packaging industry, and can prolong the shelf life of deep-processed foods such as fruits, vegetables, meat, frozen foods, cakes and the like.

The above-mentioned embodiments are intended to illustrate the objects, technical solutions and advantages of the present invention in further detail, and it should be understood that the above-mentioned embodiments are merely exemplary embodiments of the present invention, and are not intended to limit the scope of the present invention, and any modifications, equivalent substitutions, improvements and the like made within the spirit and principle of the present invention should be included in the scope of the present invention.

Claims

1. A plastic packaging material with bacteriostatic and fresh-keeping functions is characterized by being prepared from 70-99% of plastic and 1-30% of nano functional material;

the nanometer functional material is mainly prepared from the following nanometer raw materials: 1-10 parts of modified kaolin, 1-10 parts of nano zinc oxide, 1-10 parts of chitosan, 1-10 parts of starch, 1-10 parts of calcium carbonate, 1-10 parts of modified montmorillonite and 1-10 parts of anatase.

2. The plastic packaging material of claim 1, wherein the nano-functional material has at least one dimension in the range of 0.1-100 nm.

3. The plastic packaging material of claim 1, wherein the modified kaolin is obtained by ball milling modification of kaolin with hydrogen-containing silicone oil.

4. The plastic packaging material of claim 1, wherein the modified montmorillonite is obtained by ball-milling modification of sodium montmorillonite and hexadecyl trimethyl ammonium bromide.

5. The plastic packaging material as claimed in claim 3 or 4, wherein the ball milling medium is steel balls, the rotation speed is 800-1200 r/min, and the ball milling time is 1-2 hours.

6. A plastic packaging material according to claim 1, wherein said plastic comprises petrochemical-based biodegradable plastic and natural biodegradable plastic.

7. A method for preparing a plastic packaging material as claimed in any one of claims 1 to 6, characterized by comprising the steps of:

8. The preparation method of the plastic packaging material as claimed in claim 7, wherein in the blending process in the step (1), the mass percent of water is 20-45%, and the pH value is 6-7.

9. The method for preparing a plastic packaging material as claimed in claim 7, wherein a dispersing agent is further added during the grinding in step (2).

10. The method for preparing a plastic packaging material as claimed in claim 7 or 9, wherein the sieved particle size of step (2) is less than 800 mesh.